The present invention relates to a device for detecting operation of a brake pedal by which a condition of operation of the brake pedal conducted by a driver is detected and a predetermined control signal is outputted to the brake device of a vehicle so that the brake device can be operated in accordance with the demand of a driver.
In the automobiles manufactured recently, intelligence of the brake system is enhanced, for example, the anti-lock brake system and the traction control system are actively installed in the brake system.
When intelligence of the brake system is enhanced as described above, in order to operate the brake system in accordance with the demand of a driver, automobile engineers have been actively making a study of a detector for detecting operation of a brake pedal by which a condition of operation of the brake pedal conducted by a driver is detected and a predetermined control signal is outputted to the brake device.
For example, a device for detecting operation of a brake pedal shown in FIG. 5 is conventionally known, which includes a pushing force sensor 2 to detect a pushing force given by a driver, arranged in a tread portion la of the brake pedal 1.
Usually, the brake pedal 1 is elastically supported by a pedal biasing spring 3 so that a predetermined operating reaction force (brake feeling) can be obtained when a driver puts on the brake and also the brake pedal 1 can be quickly returned to the initial position when the driver's foot is separated from the brake pedal 1.
The above pushing force sensor 2 outputs an electric signal in accordance with the pushing force given by a driver.
When the brake is suddenly put on by the driver, an intensity of pushing force given to the pushing force sensor 2 is sharply increased as shown by curve A in FIG. 6. However, when the brake is gently put on by the driver, an intensity of pushing force given to the pushing force sensor 2 is gently increased as shown by curve B in FIG. 6.
Accordingly, as shown in FIG. 7, when an electric signal outputted from the pushing force sensor 2 is differentiated so that a rate of increase in the intensity of pushing force is found, that is, when inclinations of curves A and B are found, it is possible to discriminate whether it is a sudden braking operation or a gentle braking operation. When operation of the brake device is controlled in accordance with the result of discrimination, it is possible to realize the braking operation demanded by the driver.
In this connection, in FIG. 7, curve C corresponds to curve A in the case of a sudden braking operation in FIG. 6, and curve D corresponds to curve B in the case of a gentle braking operation in FIG. 6.
However, as shown on curve A in FIG. 6, minute noises n are added to an amplitude of the output signal of the pushing force sensor 2. When this output signal of the pushing force sensor 2 is differentiated, noises n are amplified as shown in FIG. 7. For the above reasons, there is a possibility that judgment of the operating condition of the brake pedal 1 is affected by the noises, for example, there is a possibility that judgment of whether or not it is a sudden braking operation is affected by the noises.
If filtering treatment is conducted on the electric signal so as to solve the above problems, judgment of the operating condition of the brake pedal 1 can be conducted more accurately. However, when filtering treatment is added to the controlling process, it takes time. As a result, a time delay is caused in the controlling time.